Starting Dec. 1, Joseph Slifka Center Executive Director Amy Aaland will take an indefinite sick leave, the center announced Wednesday.

Aaland, who has worked at Slifka for 12 of its 13 years on campus, will take time away from the center to battle breast cancer, she wrote in an e-mail to the Slifka community yesterday. Although management of the center has been shared among other administrators, her absence will nonetheless be felt both at Slifka and in the wider Jewish community at Yale, students and Slifka administrators said after the announcement.

“Despite my husband saying ‘You really should focus on your health,’ the Slifka Center has been such a source of strength for me over time,” Aaland said in a phone interview Wednesday night.

Over the past few months, administrators have transferred the task of running the center from Aaland’s sole purview to a management team of senior officials called the “mazkirut,” which may ease the transition, Aaland said.

The members of the mazkirut include Aaland, Head of Slifka Center Rabbi James Ponet, Slifka Director of Development Shana Ross and Slifka Director of Operations Rabbi Lina Zerbarini.

“Jim and I as a team have been leading Slifka for a long time,” Aaland said, expressing confidence that the mazkirut would function smoothly without her input. “We wanted and knew it needed to grow and expand, and this really felt like the best way.”

But for Hillel co-president Avi Kupfer ’10, the loss of Aaland will affect not only the operations of Slifka, but also Hillel, the largest of the undergraduate Jewish organization at Yale.

“For as long as I’ve been here, she’s been the heart of the support system that Yale Hillel has had,” Kupfer said. “On a professional level, she’s always been one of the top coordinators and advisors. On a totally separate level … she’s been incredibly important as a coordinator and supporter of Hillel. She’s really put her heart and soul into interacting with students on a daily basis.”

Aaland’s impact extends beyond Hillel to the entire population of Jews at Yale by helping with fundraising and event planning and by her mere presence in the building, Vice President for Outreach Yaron Schwartz ’11 said.

Although she will no longer be involved in the day-to-day happenings at Slifka, Aaland said she cannot imagine her life without the center.

“My heart is in the Slifka Center,” Aaland said. “The building itself is absolutely beautiful, but what draws me there is the amazing students, who I learn from all the time, whom I hope in some small way I can help as well.”

Aaland said she would continue to frequent Slifka, adding in her e-mail to the Slifka community that she looked forward to seeing students at Shabbat services and in the kosher kitchen.

Aaland noted that her decision to take a medical leave ironically coincides with the Slifka’s “bar mitzvah,” or 13th, year.

“I think the conjunction of her departure with the institution marking its bar mitzvah has a strong symbolic meaning dramatizing that the institution has come of age, and that as a vibrant institution, its strength is no longer dependent on a particular individual,” Ponet said. “The institute is now in the stage of really re-envisioning its role in the next 13 years.”

A ceremony honoring Aaland’s contributions is being planned for December, but no date or type of event has yet been set, Ponet said.